BAG-1--A NOVEL BCL-2 BINDING PROTEIN

Bcl2基因是细胞程序性死亡的阻滞剂，其表达 在很大比例的人类癌症中变得失调，包括 乳腺癌、前列腺癌和结肠腺癌、鳞癌 肺部疾病，淋巴瘤和白血病。Bcl-2基因的过量生产 蛋白质已被证明能显著增强肿瘤细胞对 几乎所有的化疗药物和放射都会导致细胞死亡， 这表明bcl2在某种程度上可以被视为一种多药- 抗性基因。Bcl2基因的产物是一个完整的膜 驻留在线粒体膜外的蛋白质，核 包膜和内质网。预测的氨基酸序列 然而，这种蛋白质的生物化学机制并不能说明 行动。 为了进一步了解Bcl-2的机制，一种相互作用的克隆 使用技术鉴定编码bcl2结合蛋白的cDNA， 导致了一种新的蛋白质BAG-1的发现。重组BAG-1 多种方法显示蛋白质能与Bcl2特异性结合。 在体外，这两种蛋白可以从哺乳动物的免疫共沉淀中获得 细胞。免疫显微镜显示BAG-1和Bcl2可能存在于 至少部分在相同的亚蜂窝位置。共转染BAG-1基因 编码Bcl1和Bcl2的表达载体可增强抑制作用 与BAG-1或Bc1-2单独作用相比，BAG-1和Bc1-2对细胞凋亡的抑制作用更强。人形袋子-1 基因定位于染色体9p13，一个可能与遗传有关的区域 提示发育细胞死亡有缺陷的症状。 对其结构、表达和功能的全面考察 对Bag-1基因进行了初步研究，包括：(1) 人和小鼠Bag-1基因的外显子/内含子组织； BAG-1蛋白的亚细胞定位及其在体内的分布 生产；(Iii)BAG-1与Bc l-2结合的特定部位以及 这种相互作用对Bcl-2功能的重要性；(Iv)生化 BAG-1蛋白的性质；(V)BAG-1的体内功能 通过创造转基因和基因敲除小鼠；以及(Vi) 肿瘤和遗传综合征中BAG-1基因改变的可能性 映射到9p13。

The bcl-2 gene is a blocker of programmed cell death, whose expression becomes dysregulated in a large proportion of human cancers, including adenocarcinomas of the breast, prostate, and colon, squamous carcinomas of the lung, and lymphomas and leukemias. Over-production of the Bcl-2 protein has been shown to make tumor cells strikingly more resistant to cell death induced by nearly all chemotherapeutic drugs and radiation, suggesting that bcl-2 can in some ways be viewed as a multidrug- resistance gene. The product of the bcl-2 gene is an integral membrane protein that resides in the outer mitochondrial membrane, nuclear envelope, and endoplasmic reticulum. The predicted amino-acid sequence of this protein however has failed to suggest a biochemical mechanism of action. To gain further insights into Bcl-2 mechanisms, an interaction cloning technique was used to identify cDNAs that encode Bcl-2 binding proteins, leading to the discovery of a novel protein, BAG-1. Recombinant BAG-1 protein was shown by several methods to specifically bind to Bcl-2 in vitro, and the two proteins could be co-immunoprecipitated from mammalian cells. Immunomicroscopy suggests that BAG-1 and Bcl-2 may reside at least in part in the same subcellular locations. Co-transfection of BAG- 1 and Bcl-2-encoding expression plasmids results in enhanced suppression of apoptosis compared to either BAG-1 or Bcl-2 alone. The human BAG-1 gene maps to chromosome 9p13, a region possibly involved in hereditary syndromes that suggest a defect in developmental cell death. A comprehensive investigation of the structure, expression, and function of the BAG-1 gene is proposed, including determination of (i) the exon/intron organization of the human and mouse BAG-1 genes; (ii) the subcellular location of the BAG-1 protein and its in vivo patterns of production; (iii) the specific sites where BAG-1 binds to Bcl-2 and the importance of this interaction for Bcl-2 function; (iv) the biochemical properties of the BAG-1 protein; (v) the in vivo function of BAG-1 through creation of transgenic and knock-out mice; and (vi) the possibility of alterations in BAG-1 in cancers and hereditary syndromes mapped to 9p13.